Position and posture adjustment method

1. A position and posture adjustment method for adjusting a position and a posture of an arm distal end portion of a robot with respect to a workpiece, using a measuring device attached to the arm distal end portion and a marker having a head cut conical shape arranged in the workpiece, the measuring device including three laser displacement gauges each arranged at vertexes of an equilateral triangle and having optical axes each set to intersect at a vertex of a trigonal pyramid having the equilateral triangle as a base, the position and posture adjustment method comprising: a provisional teaching step of teaching the robot a predetermined position and a predetermined posture of the workpiece; a marker installation step of installing the marker at the predetermined position of the workpiece with the predetermined posture; an initial movement step of moving the arm distal end portion such that irradiated positions of the three laser displacement gauges are arranged within an end surface of the marker, using a result of the provisional teaching step; a posture modification step of moving the arm distal end portion such that measured values of the three laser displacement gauges become close to each other while maintaining a state in which the irradiated positions of the three laser displacement gauges are arranged within the end surface; an approach step of bringing the arm distal end portion close to the marker along an axis of the trigonal pyramid such that a diameter of a virtual circle passing through the irradiated positions of the three laser displacement gauges in a virtual plane including the end surface becomes larger than a diameter of the end surface; an alignment step of causing the axis of the trigonal pyramid and an axis of the marker to coincide with each other by moving the arm distal end portion parallel along a plane perpendicular to the axis of the trigonal pyramid such that the measured values of the three laser displacement gauges become close to each other; and a positioning step of adjusting the position of the arm distal end portion by moving the arm distal end portion along the axis of the trigonal pyramid.

2. The position and posture adjustment method according to claim 1 , wherein the initial movement step includes a provisional teaching operation execution step of setting the arm distal end portion to a predetermined position and posture, using the result of the provisional teaching step, an end surface search step of moving the arm distal end portion such that all the measured values of the three laser displacement gauges become values close to one another, and a separation step of separating the arm distal end portion from the marker along the axis of the trigonal pyramid such that the irradiated positions of the three laser displacement gauges are arranged within the end surface.